Search 1,000 of PHOTOS Katherine Marie Heigl (born November 24, 1978) is an American actress. She was best known for her role as Dr. Izzie Stevens on ABC's Grey's Anatomy from 2005 to 2010. She has also starred in films such as Knocked Up, Zyzzyx Road, 27 Dresses, The Ugly Truth, Killers, and Life As We Know It.